Some tomites transformed from trophonts or released by asymmetric dividers swim rapidly to seek more food patches, transforming back into trophonts when they find new food patches and repeating the above processes. The quickly dispersing tomites, the tolerating Selleckchem Smoothened Agonist resting cysts, and the diverse reproductive strategy may enable G. trihymene to identify and dominate enough food patches and survive in the coastal water U0126 cost community. Phylogenetic position of G. trihymene, and asymmetric division G. trihymene groups with typical scuticociliates with high bootstrap support and posterior

probability, though the precise relationships within the clades remain unresolved (Figure 4). In addition, G. trihymene has high SSU rDNA pair-wise identity with Anophryoides haemophila (96%), the scuticociliate

causing the “”Bumper car disease”" of American lobsters and Miamiensis avidus (96%), a polyphenic, parasitic ciliate, which causes diseases in fish [27, 28]. Our result supports the monophyly of scuticociliatia, despite what was found in earlier studies utilizing a previously reported G. trihymene SSU rDNA sequence [GenBank Accession No.: AY169274] [29, 30], which we believe to be erroneous. AY169274 shares great similarity with SSU sequences of some flagellates, e.g. it has Tariquidar 96% identity with the 18S rDNA sequences of the nanoflagellate Spumella sp. GOT220 [GenBank Accession No.: EF027354]. In line with our interpretation, the most recent study on morphology and morphogenesis of G. trihymene (performed by the same group that submitted the Clostridium perfringens alpha toxin previous Gt SSU rDNA sequence) showed that it is indeed a typical scuticociliate [22]. Asymmetric divisions, similar to those in G. trihymene, occur in certain apostome and many astome ciliates (see phylogenetic position in Figure 4), though the details of division had never been studied using continuous microscopy [5]. Such asymmetric dividers were called catenoid colonies in these host-dependent ciliates. Asymmetric dividers were

so named in the present study to emphasize the difference between the two filial cells. As in the asymmetric division of G. trihymene in Figure 2A, long cell chains in the parasitic and commensal astome and apsotome ciliates are formed by repeated incomplete divisions without separation of the resulting filial products, after which some subcells are fully or partially pinched off. These subcells require subsequent metamorphosis to regain the form typical of the normal trophont stage of the life cycle [3, 5]. The results of the phylogenetic analysis suggest that complex life cycles including asymmetric division are either 1) an ancestral feature of these three groups that has been modified, lost, or not yet discovered in other free-living species, or 2) a convergent trait that has arisen multiple times independently in these closely related taxa.